The invention relates to a high pressure pump as set forth in EP 0 481 964 A2.
High pressure pumps of this kind are used for fuel injection in diesel engines. They are disposed between a low pressure container and a high pressure reservoir (rail) and ensure that there is a satisfactory quantity of fuel at a sufficient high pressure in the high pressure chamber in order to supply fuel to the working cylinders of the engine in a controlled manner via injection valves.
In the known high pressure pump, a solenoid valve, which is open when without current, is disposed between the low pressure container and the pump cylinder. It is closed by a current pulse to establish the beginning of the high pressure delivery. Otherwise, it remains unexcited. To close the solenoid valve, relatively intense forces must be brought to bear by the magnet, wherein the force of the valve spring that counteracts the closing must be overcome. As a result, the cost and current requirement of the magnet are relatively high.
In conventional injection systems with parallel supply of a number of pump working chambers from the low pressure circuit, there is already a so-called suction throttle regulation in which the pump is operated with variable partial guidance. However there is the danger of cavitation through the formation of voids, and in addition, a very rapid pressure buildup is produced at the onset of delivery.
Similar disadvantages also arise in a suction throttle regulation when a solenoid valve and with it a solenoid valve metering are used instead of the throttle.